Positive displacement motors (PDMs) are widely used in the oil and gas industry as an adjunct for drilling a hole in earthen formations. The PDM uses pressure and flow of the drilling fluid to turn a rotor within a stator. The rotor then turns a drill bit which removes earthen cuttings, creating the hole. The drilling fluid then captures the earthen cuttings and removes them from the hole. When drilling with a PDM, the drill string does not have to be rotated to drill (as is the case with conventional drilling) and this allows the drill string to be oriented, resulting in directional drilling.
If one could add a percussive force to the drill bit on the PDM, it is believed that the rate of drilling penetration could be significantly increased, the required weight on bit could be significantly reduced and torque required to turn the drill bit could be significantly reduced. All in all, a “percussionized” PDM should be an efficient drilling tool.